In the manufacture of tetrabromo-bisphenol-A, the end product is usually recovered from the bromination reaction by crystallization from solvent. The remaining mother liquor generally contains between 2-15% solids, constituting brominated phenolic material which is substantially tetrabromo-bisphenol-A referred to as TBBA. However, other brominated phenolic products are also present as impurities in the mother liquor, and make further recovery of desited tetrabromo-bisphenol A in a reasonably pure form extremely difficult. These impurities generally comprise brominated bisphenol-A at various stages of bromination, brominated phenols resulting from the cleavage of the bisphenol, and other small amounts of bromine containing oxidation products produced by side reactions during the bromination process. When the mother liquor of the recovered pure tetrabromo-bisphenol-A (TBBA) is evaporated to dryness the residue is a dark coloured product containing about 57-60% bromine comprising the impurities and tetrabromo-bisphenol-A (TBBA) mixed together and melting at about 70-80.degree. C.
Tetrabromo-bisphenol-A (TBBA) is used as a flame retardant additive or as an intermediate in the preparation of flame retardant polymers. As such it has been reacted with polycarboxylic acids to form polyesters, it has been used in the preparation of flame retardant polycarbonate resins, and it has also been used in flame retardant epoxy resins by incorporating it as a replacement or partial replacement for bisphenol-A in the resins. For these purposes it is generally desirable to use a high grade TBBA, and the manufacturers of TBBA have attempted to optimize their processes to give high purity TBBA and reduce the amount of waste residue which has to be discarded. U.S. Pat. Nos. 3,546,302; 3,182,088; 3,234,289; 3,367,007 and Gt. Brit. Pat. No. 1,316,415 among others, describe processes for preparing TBBA.
Generally, in the process for preparing brominated bisphenols, the mother liquor remaining after crystallization of product, and which comprises usually an organic solvent, is distilled and the residue disposed of. However, the residue contains phenolic and brominated phenolic products which for ecological reasons require special disposal consideration. Furthermore, these residues in some processes contain lacrymatory impurities which complicate the disposal problem.